Current-sensing time-limit motor acceleration relay



April 14, 1970 c. A. SCHURR CURRENT-SENSING TIMELIMIT MOTORACCELERATION- RELAY Filed Sept. 20, 1967 2 sneaks-Sheet 2 UM A 'Hlh.

/NVENTO/?. 'CHA/?LE$ ALLA/V SCHU/PR United States Patent U.S. Cl. 335-6313 Claims ABSTRACT OF THE DISCLOSURE The relay has a contact-carryingtube movable linearly in one direction, within an annular space betweenan inner magnetic core and outer coil-carrying spool, in response toflux change produced by current in the coil. Return movement of the tubeis caused by gravity and is retarded by the flux. The core and spool arepositioned with respect to each other by complementary annular shoulderson the core and the spool. The core and spool are secured in thisposition and to a frame of the relay by engagement of an upper edgeportion of the spool and a lower conical surface on the core withrespective cooperating parts of the frame and a support plate which issecured to the frame.

BACKGROUND OF THE INVENTION Field of the invention Aninductively-actuated electromagnetic motor acceleration relay whereinthe movement of a contact-carrying member is inductively retarded toprovide a time delay interval which varies in response to variations inthe current flowing in an operating coil of the relay and wherein theforce of inductive retardation is time-overrideable by the force ofgravity acting upon the contactcarrying member to cause operation of therelay even when there is little or no variation in the current flowingin the coil.

Description of the prior art Various motor acceleration relays haveheretofore been provided for controlling the commutation of the startingresistance in a motor circuit so that the current taken by the motorduring acceleration does not exceed predetermined values.

One type of acceleration relay is described in U.S. Patent No.1,980,736, issued Nov. 13, 1934 and in U.S. Patent No. 2,073,382, issuedMar. 9, 1937. Relays of this type are used in the so-called time-currentsystem of motor acceleration and, when adjusted to provide properacceleration of the motor under predetermined operating conditions, alsoprovide, without change or adjustment, proper acceleration underdifferent or even abnormal operating conditions.

As used in a motor acceleration system, these relays normally delay thesuccessive energization of resistance commutating switches for periodsdetermined by the magnitude of the current flowing to the motor, but ifthe motor fails to accelerate, or accelerates too slowly, the

relays cause the next successive switch to be energized "ice open at therear for ease of mounting on the front of a control panel. A spoolmember surrounded by an electromagnetic winding or coil is retained inthe frame by a collar which is threaded into the top of the frame andurges the spool member against the bottom of the frame. The core of theprior relay has a lower threaded portion which is received, through acentral axially-disposed opening in the spool member, in a complementarythreaded opening in the bottom of the frame. A jam-nut, received on thethreaded portion of the core and turned up against the outside face ofthe bottom of the frame,

secures the core in position. The threaded connections provided in theprior relay not only add to the expense of manufacture, but also requirethat considerable care be exercised in assembly of the relays so as toobtain proper alignment of the relay components relative to each other.

An additional disadvantage of the prior current-sensing time-limit relayis that the coil is arranged for connection only from the rear of thepanel on which the relay is mounted. The leads from the coil extendrearwardly through the rear opening in the frame and through themounting panel for connection to other wiring on the rear of the panel.In controllers using the prior relay, the

wiring between the components and the incoming or source leads, as wellas the load leads, are connected on the rear of the panels. This isacceptable where floor space is ample and where the controller can bespaced from adjacent objects to permit convenient access to a workmanfor making connections on the rear of the panel.

Recently, however, demand has increased for controllers havingelectrical components arranged for wiring from the front of the panel.The prior time-current relay does not lend itself to front wiringbecause of the difficulty of bringing the heavy coil leads out to thefront of the panel.

SUMMARY OF THE INVENTION A current-sensing time limit motor accelerationrelay in accordance with present invention has a spool member which hasa downwardly directed shoulder in its central opening intermediate theends thereof. The magnetic core of the relay is provided with anupwardly directed annular shoulder intermediate its ends and has ashallow conical portion at its lower end. The shoulders on the core andspool member position the core and spool with respect to each other. Theconical portion of the core is received in a circular opening in asupport plate which is removably secured to the bottom portion of aframe of the relay so that an upper edge of the opening engages thesurface of the conical portion. In this manner, when the support plateis drawn into secured relationship with the frame, it urges the core andthe spool member into firmly secured relationship with each other and atthe same time urges an upper portion of the spool member firmly againstthe top portion of the frame. Thus, the improved structure of thisinvention eliminates the disadvantageous threaded connections betweenthe core and frame of the prior art device and also inherently assures aproperly aligned assembly, which proper alignment was achieved in therelay of the prior art only by selective adjustment.

The present invention additionally comprises a coil having terminalswhich are brought out toward the front of the relay thereby permittingthe relay to be used on a controller where the wiring is arranged on thefront side of the controller panel. Portions of the terminals extendoutwardly through respective openings in a front cover of the relay, andthe portions of the terminals interior of the cover receive a pair ofbolts which are threaded into the terminals from the outside of thecover 3 to assist in supporting the coil. In this manner, the structureof the present invention provides a front-connectible relay thereby tosolve an additional problem previously existent in the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of anelectromagnetic relay in accordance with this invention;

FIG. 2 is an exploded perspective view of the relay of FIG. 1;

FIG. 3 is a top plan view of the relay of FIG. 1, a contact enclosingcover being removed;

FIG. 4 is a front plan view of the relay of FIG. 1, a portion of thecontact cover and a contact housing being broken away; and

FIG. 5 is a sectional view taken generally along the line 5--5 of FIG.4.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, anelectromagnetic currentsensing time-limit acceleration relay inaccordance with this invention comprises a base and a magnetic fluxconducting frame assembly 11. The frame assembly includes a pair of sideplates 14 and 15 and an upper wall or top plate 16, the side platesbeing preferably welded, one at each side of the top plate 16, as bestillustrated in FIGS. 2 and 4, to form the generally U-shaped frameassembly. The frame assembly 11 is mounted on the base 10 by suitablenuts received on fastening means such as threaded weld screws 17a whichare affixed one to each of the side plates 14 and 15 and which arereceived through mounting holes in the base 10. An additional bolt 19(FIG. 5) threaded into the top plate 16 assists in firmly securing theframe assembly to the base.

An operating coil 20 comprising a winding 21 encapsulated in aninsulating compound 22 such as epoxy has a cylindrical opening 23extending therethrough along the axis of the winding. A pair of powerterminals 24 and 25 are mechanically and electrically secured to theends of the winding 21. A nonconductive generally tubular-shaped spool26 having an axially-aligned opening and an outer flange 27 near one ofits ends is received in the opening 23 of the coil 20, as bestillustrated in FIG. 5. The outside diameter of the spool 26 and thediameter of the coil opening 23 are dimensioned to provide adequateclearance for the spool to be easily inserted into the opening butwithout any excessive looseness.

As illustrated in FIG. 5, the inner wall of the spool 26 has aninwardly-directed annular flange portion 29 defining a section of thespool of reduced inner diameter with respect to the diameters of anupper spool portion 30 and a lower spool portion 31 on either side ofthe flange portion 29. A generally cylindrically-shaped magnetic fluxconducting core 32, preferably fabricated of cold-rolled steel andhaving an annular shoulder 34 defining a lower core portion 35 of largerdiameter than an upper core portion 36 disposed above the shoulder 34,is received in the opening of the spool 26. The diameter of the uppercore portion 36 and the inner diameter of the spool 26 at its annularflange portion 29, and likewise the diameter of the lower core portion35 and the inner diameter of the lower spool portion 31, are dimensionedto provide a slight allowance so that a clearance fit without excessivelooseness results between the flange portion 29 and lower portion 31 ofthe spool and the upper and lower core portions 35 and 36.

Thus, the coil 20, the spool 26, and the core 32 are positionedcoaxially with respect to each other, the shoulder 34 of the corecooperating with a downwardly directed shoulder of the inner flangeportion 29 to limit the extent of entry of the core 32 into the spool26, and the outer flange 27 of the spool cooperating with the top edgeof the coil 20 to limit the extent of entry of the spool 26 into theopening 23 of the coil.

The top plate 16 of the frame assembly 11 is provided with a circularopening 37 of approximately the same diameter as the inside diameter ofthe upper portion 30 of the spool 26 and, on the undersurface of the topplate, a shallow annular positioning recess 39 (FIG. 5) surrounds theopening 37. The positioning recess 39 serves to locate and to maintainin proper alignment the upper edge portion of the spool 26 when thespool, coil, and core are secured in the frame assembly 11 as will beexplained.

A supporting means such as the core support plate 40, best'illustratedin FIG. 2, and having a circular opening 41 of materially lesserdiameter than the diameter than the diameter of lower core portion 35,is secured to the frame assembly 11 by suitable nuts received onfastening means such as threaded weld screws 17b which are affixed tothe side plates 14 and 15 and extend through holes 42 in the supportplate 40. The end of the core 32 at the lower core portion 35 isprovided with a shallow conical portion 44, best shown in FIG. 5, whichfacilitates proper alignment of the core within the opening 37 of thetop plate 16. When the support plate 40 is assembled in securedrelationship with the frame assembly 11, the upper edge of the circularopening 41 in the support plate bears against the conical portion 44 ofthe core 32. The annular shoulder 34 of the core, in turn, bearsupwardly upon the downwardly-directed shoulder of the inner flangeportion 29 of the spool 26 thereby to urge the upper end of the spoolfirmly against the top plate 16 in the positioning recess 39. Thus theassembly of the spool 26 and the core 32 is firmly secured to the frameassembly 11 by the support plate 40 without the need for any fasteningmeans other than the nuts and cooperating weld screws 1711 by which theplate 40 is drawn into the frame assembly 11.

The diameter of the upper core portion 36 is materially less than theopening of the upper portion 30 of the spool 26, thereby leavingclearance space between the upper portions of the core and spool.Likewise, a clearance space is present between the upper core portion 36and the top plate 16 thereby to provide an air-gap in the magneticcircuit of the relay. A non-magnetic tubular member such as the inductortube 45, which may be formed of aluminum or hard-drawn copper, isslidably disposed in the aforementioned clearance spaces surrounding theupper core portion 36. The tube 45 carries a contact bridge assembly 46comprising a pair of electrically-connected movable bridging contacts 47and an insulating carrier 49. In the preferred embodiment, the contactbridge assembly 46 is mounted on the tube 45 by means of a binding postand screw fastener 50, the assembly 46 being slidably disposed on thebinding post together with a helical compression spring 51 whichnormally urges the contact bridge assembly toward the top end of theinductor tube 45 as shown in FIGS. 4 and 5.

A pair of guide rods 52, fixedly secured in the top plate 16, cooperatewith a pair of openings 54 (FIG. 3) in the carrier 49 to guide thecontact bridge assembly so as to assure proper alignment of the movablecontacts 47 with a pair of complementary stationary contacts carried bya pair of spring steel support members 55. Although the stationarycontacts are not visible in the drawings, they are situated as viewed inFIG. 3, at the ends of the support members 55 directly beneath theirassociated movable bridging contacts 47. When the relay is mounted foruse in a motor controller, it is positioned so that the tube 45 isbiased by gravity to a position wherein the movable bridging contacts 47engage their associated stationary contacts.

The contact support members 55 are fixedly mounted by suitable screwfasteners 56 to a contact housing 57 which also supports a pair ofterminal members 58. At one end of each terminal member 58 there isprovided suitable means for connecting wires from an external controlcircuit to the terminal members. The other end of the member 58 isreceived under one of the screw fasteners 56 and is in electricallyconductive relationship with its associated support member 55 and one ofthe stationary contacts. The housing 57 is secured to the top plate 16by a pair of screws 60 (FIG. 3).

A cover 61 is provided for the housing 57 to shield the contacts andother relay components from dust and other air-borne contaminants. Apair of spring clips 62 affixed to the housing 57 cooperates withlatching shoulders on the cover 61 to removably secure the cover to thehousing. An additional cover 64 is secured to the remainder of the relayassembly by a tab portion 65 of the cover 64 which cooperates with aslot 66 in an extension 67 of the support plate 40 and by a bolt 70which is received through the cover 64 in the top plate 16.

When the cover 64 is secured in place in the relay assembly, portions ofthe power terminals 24 and 25 of the coil 20 extend through respectiveholes in the cover thereby to provide access to the coil terminals fromthe front side of the relay. As shown in FIGS. 14, these outwardlyextending portions of the terminals 24 and 25 are drilled and tapped toreceive bolt fasteners (not shown) of a pair of power leads from anexternal circuit. As shown in FIG. 2, the terminals 24 and 25 are alsodrilled and tapped to form threaded openings 24a and 24b therein,respectively; a pair of bolts 71 (FIG. 1) received through the cover 64in the openings 24a and 24b assists in supporting the coil 20.

The relay functions as described more fully in US. Patents 1,980,736 and2,073,382 to control the commutation of resistance in a motor controlcircuit.

The relay may be considered as a current transformer with a movablesecondary comprising the inductor tube 45 as a single turn winding. Theprimary of the transformer is the winding 21. When current isestablished in the winding 21, the growing direct current induces asecondary current in the tube 45. Repulsion between the tube 45 and thewinding 21 causes the tube to move upwardly thereby to separate themovable and stationary contacts. When the current ceases to grow in theoperating winding 21, there is no secondary current in the inductor tube45, and the tube 45 begins to fall down through flux in the air gapbetween the upper core portion 36 and the top plate 16.

The flux in the air gap varies in strength directly in accordance withthe strength of the current in the winding 21. The rate of return of themovable tube 45 is governed by the strength of the flux in the air gap,being slower when the flux strength is great and being more rapid whenthe flux strength is small. It is clear therefore that the rate of thereturn of the inductor tube 45 and hence the length of time required toclose the contacts controlled by the movable tube are modified byvariations in the strength of the current in the winding 21.

Motion of the tube 45 in the magnetic field causes electric currents tobe generated in the tube, opposing the force of gravity tending to movethe tube downwardly thereby retarding its downward movement, by which atime delay interval is obtained. At the end of the downward stroke ofthe tube 45, the movable and stationary contacts are closed.

As previously mentioned, the tube 45 may be formed of aluminum orcopper. The use of an aluminum tube in the same relay in place of acopper tube provides, without further adjustment or alteration in therelay structure, an increased time delay interval owing to the decreasedelectrical conductivity of aluminum as compared to copper.

I claim:

1. In an electromagnetic current-sensing time-limit relay including amagnetic frame having an upper wall, a magnetic core disposed influx-conductive relationship with said frame, at least one stationarycontact, a nonmagnetic current-conductive tubular member slidablysupported about said core and normally biased toward one position, atleast one movable contact carried by said tubular member and inengagement with said stationary contact when said tubular member is insaid one position, a coil including a winding surrounding said core andoperable upon energization to produce a magnetic flux which causes thetubular member to move-quickly away from said one position towardanother position wherein said movable contact is out of engagement withsaid stationary contact, said tubular member, after movement toward saidanother position and upon continued energization of said winding, beingoperable to return slowly to said one position, the improvementcomprising a nonconductive generally tubular-shaped spool member havingan upper portion adapted to bear against said upper wall of said frameand having a downwardly-directed shoulder portion disposed in anaxially-aligned opening of the spool member intermediate the ends ofsaid opening, said core being provided with an upwardly-directedshoulder portion intermediate its ends and having a shallow-conicalportion at its lower end, core supporting means removably secured tosaid frame and disposed in spaced relation to said upper wall and havinga circular opening therein of materially lesser diameter than the basediameter of said conical portion, said core being coaxially receivedwithin the opening of said spool member with the shoulder portion ofsaid core engaging the shoulder portion of said spool member, and theconical portion of said core being received in the circular opening ofsaid supporting means so that an upper edge of the circular openingbears against the surface of said conical portion whereby, when thesupporting means is drawn into secured relationship with said frame,said core and spool member are firmly secured relative to each other andto said frame.

2. A relay according to claim 1 wherein a contact housing is removablysecured to said upper wall of said frame.

3. A relay according to claim 1 wherein said core supporting means has aforwardly-directed extension having a slot therein and wherein saidrelay additionally includes a front cover having a downwardly extendingtab portion receivable in said slot, said cover being secured to saidrelay at a front side thereof by receipt of said tab portion in the slotof said extension and by a separate fastener means fastening said coverto said upper wall of said frame.

4. A relay according to claim 1 wherein the tubular member has agenerally annular cross-section and is formed of a material selectedfrom the group consisting of copper and aluminum.

5. A relay according to claim 1 wherein said frame is generally U-shapedand said upper wall comprises the bight portion of the U.

6. A relay according to claim 5 wherein said core, said frame, and saidcore supporting means define two magnetic flux paths, each path having acommon portion extending through said core, one of said paths extendingin loop fashion through said core, one portion of said core supportingmeans, one leg of said U-shaped frame and one portion of the upper wallof said frame, and the other of said paths extending in loop fashionthrough said core, the other portion of said core supporting means, theother leg of said U-shaped frame and the other portion of said upperwall, and wherein said magnetic flux path has an air gap therein betweensaid upper wall and the upper end of said core.

7. A relay according to claim 1 wherein said upper wall has a circularopening therein, said opening being of substantially the same diameteras the diameter of the opening of said spool member, said upper wall hasa shallow recess surrounding the opening in the upper wall and facingtoward said spool member, and said upper portion of said spool member isreceived in said recess whereby the openings in said wall and spool aremaintained in substantial coaxial alignment, said core being disposedsubstantially coaxially within said openings.

8. A relay according to claim 7 wherein said shoulder portion of saidcore defines upper and lower core portions,

said upper core portion having a diameter materially less than thediameter of the openings in said spool and said upper wall thereby todefine a clearance space between said upper core portion and said upperwall and spool, said tubular member being slidably disposed in saidclearance space about said upper core portion.

9. A relay according to claim 1 additionally including a base mounted tosaid frame at a rear side of said relay, and wherein said winding has apair of forwardly-facing terminal members at a front side of the relay.

10. A relay according to claim 9 additionally including a cover securedto said relay at the front side thereof, openings in said cover alignedwith said terminal members, respectively, so as to permit a portion ofsaid terminal members to extend therethrough exteriorly of the cover,fastening means receivable through said cover and removably secured tothe portion of the terminal members interior of the cover thereby tomaintain said terminal members in fixed relationship with said cover andto assist in supporting said coil.

11. In an electromagnetic current-sensing time-limit relay including abase, a magnetic frame mounted on a front side of said base by meanssecuring a rear side of the frame thereto, a generally cylindricalmagnetic core disposed in flux-conductive relationship with said frame,at least one stationary contact, a non-magnetic currentconductivetubular member slidably supported about said core and normally biasedtoward one position, at least one movable contact carried by saidtubular member and in engagement with said stationary contact when saidtubular member is in said one position, and a coil including a windingsurrounding said core and operable upon energization to produce amagnetic flux which causes the tubular member to move quickly away fromsaid one position toward another position wherein said movable contactis out of engagement with said stationary contact, said tubular member,after movement toward said another position and upon continuedenergization of said Winding, being operable to return slowly to said tosaid one position, the improvement comprising means including aremovable support plate clamping said core firmly in place With respectto said frame, said winding having a pair of terminal members spacedfrom said base and disposed forwardly thereof, so that said terminalmembers are accessible from the front side of the base.

12. A relay in accordance with claim 11 wherein a cover is secured tosaid relay at the front side of the frame, said cover having twoopenings therein aligned with said terminal members, respectively, aportion of each terminal member extending extending exteriorly of thecover through its associated opening and the portion of each terminalmember interiorly of the cover receiving a bolt fastener threaded intothe terminal member from the exterior of the cover to assist insupporting said coil.

13. In an electromagnetic current-sensing time-limit relay including abase, a magnetic frame mounted on a front side of said base by meanssecuring a rear side of the frame thereto, a generally cylindricalmagnetic core disposed in flux-conductive relationship with said frame,at least one stationary contact, a non-magnetic currentconductivetubular member slidably supported about said core and normally biasedtoward one position, at least one movable contact carried by saidtubular member and in engagement with said stationary contact when saidtubular member is in said one position, and a coil including a windingsurrounding said core and having a pair of terminal members adapted forconnection to a source of power, said winding being operable uponenergization to produce a magnetic flux which causes the tubular memberto move quickly away from said one position toward another positionwherein said movable contact is out of engagement with said stationarycontact, and said tubular member, after movement toward said anotherposition and upon continued energization of said winding, being operableto return slowly to said one position, the improvement comprising acover secured to said relay at the front side of the frame, saidterminal members being spaced from said base and disposed forwardlythereof so as to provide access to said terminal members from the frontside of said base, and said cover having two openings therein alignedwith said terminal members, respectively, a portion of each terminalmember extending exteriorly of the cover through its associated openingand the portion of each terminal member interiorly of the coverreceiving a bolt fastener threaded into the terminal member from theexterior of the cover to assist in supporting said coil.

References Cited UNITED STATES PATENTS 1,980,736 11/1934 Trofimov 335-632,073,382 3/1937 Trofimov 318392 3,238,329 3/1966 Russo 335-132 BERNARDA. GILHEANY, Primary Examiner H. BROOME, AssistantExaminer US. Cl. X.R.

